Okay..I'm late to this on account of having been away for a couple of days, but let me go ahead and throw my own 2-cents into this conversation.
Adam here was not the only one who took exception to this situation. Apparently a whole lot of people online got bent out of shape about it, and tried to gatekeep Metallica, to the point that they basically released a brief statement telling people to knock it off.
...to that I'll only add that while I support at least some small degree of gatekeeping in any hobby, because fuck social parasites, at the end of the day Metallica isn't the hill to die on. That war was over a long time ago, with the release of the black album. At this point you'd have to be fresh off the spaceship to not know who they were, so I'm honestly confused what people were trying to keep secret.
Honestly though, it's not worth getting upset every time some brain dead Kardashian is seen wandering around with a Slayer shirt on. The vast majority of these people aren't going to get any further than the most well known names that they know from the radio. They're not metal fans, and most likely never will be. More importantly though, is that they're not really trying to be either, and because of that they affect nothing.
...and that comment about "touching grass" has nothing to do with drugs. It means you need calm down and get some perspective